1. Field of the Invention
The present invention relates to door locking devices, and more particularly to a doorknob lock apparatus that is independently operable by dial entry of a combination or by a key.
2. Description of the Related Art
The need for reliable door locking systems for use at businesses and residences is widely recognized. It is also recognized that a lock capable of operation using a combination or a key offers versatility and convenience over common cylinder locks operable by key only. Consequently, efforts have been made to provide such a lock, as evidenced by prior art U.S. Pat. Nos. 3,353,383; 4,936,122; 5,113,675; and 5,475,996.
While perhaps suitable for specialized applications, the lock mechanisms described in the prior art generally require significant modification or replacement of the existing door and/or lockset. Even in prior art lock mechanisms that are capable of use with an existing lockset, installation is difficult and often requires cutting holes into the door, attaching mounting plates, installing wires, and performing other time consuming and costly steps.
Many electro-mechanical combination/key lock systems of the prior art, for example that of U.S. Pat. No. 4,936,122, require a battery power source having a finite lifetime, such that malfunction occurs when the battery is unable to properly energize the system.
Accordingly, it is a principal object of the present invention to provide an improved convenient lock apparatus employing both key and combination actuating mechanisms by means of which the lock apparatus can be operated either by using a key or by entering the combination.
It is another object of the present invention to provide an improved lock apparatus that fits within the small volume allotted for prior art cylinder lock mechanisms.
It is yet another object of the present invention to provide a combination lock apparatus wherein the combination can be changed quickly and easily without disassembling the lock apparatus.
It is a further object of the present invention to provide a lock apparatus that is retrofittable or adaptable to a doorknob, deadbolt, locker, desk or the like.
It is a further object of the present invention to provide a lock apparatus wherein cam rings for combination operation are automatically scrambled before or as the lock apparatus is re-locked.
It is a further object of the present invention to provide an improved lock apparatus that avoids complicated and costly production and that is easy to assemble.
It is a further object of the present invention to provide a lock apparatus operable by combination or key wherein the combination cannot be determined from a key.
It is a further object of the present invention to provide an improved lock apparatus having an output nut for simple adaptation of the lock apparatus to an existing cylinder lock mechanism.
It is yet a further object of the present invention to accomplish the above objects in a completely mechanical lock apparatus that does not rely upon electrical devices requiring a power source.
In view of these and other objects that will become apparent to the reader, an improved lock apparatus of the present invention generally comprises a frame having an axially extending cylinder bore therethrough, a cylinder plug partially received by the cylinder bore having a keyhole, and a dial mounted coaxially about a front portion of the cylinder plug for combination entry. A front portion of the cylinder plug protrudes from the dial to form a knob, and an output nut is threadably mated with a rear end of the cylinder plug. A plurality of axially spaced detent wafers is slideably held within a plurality of respective radial slots in the cylinder plug, and each detent wafer is spring-biased to engage a primary keyway in the frame to prevent rotation of the cylinder plug relative to the frame. The arrangement defines a predetermined rotational reference orientation of the cylinder plug relative to the frame for maintaining a locked condition. The detent wafers are withdrawn from the primary keyway when a key is inserted in the keyhole, thereby allowing the cylinder plug to be rotated from its reference orientation. The cylinder plug rotation is transmitted through the output nut to move a locking member and achieve an unlocked condition.
The detent wafers are also withdrawn from the primary keyway by entry of a predetermined combination of numbers using the dial. The dial is operably connected to the wafers by a plurality of cam rings arranged about the frame, each cam ring having a cam surface for radially depressing an associated push pin communicating through the frame to one or more detent wafers. The dial rotationally drives a first cam ring adjacent thereto, and the first cam ring serves to drive a next adjacent cam ring, and so on, such that when the combination is entered in the correct manner the cam surface of each cam ring is in depressing engagement with an associated push pin to remove the plurality of detent wafers from the primary keyway.
A cam tube is provided about the cam rings and coupled by way of a ratchet mechanism to the cylinder plug so that the plurality of cam rings is in a scrambled state whenever the lock apparatus is re-locked. In the preferred embodiment, the cam tube includes an internal toothed portion adjacent its rear end, and a plurality of axially elongated slots angularly spaced about cam tube forward of the internal toothed portion. A plurality of spring plungers is mounted at angularly spaced intervals about the frame to engage toothed portion to provide suitable resistance to rotation of the cam tube relative to the frame. A carrier mounted on the cylinder plug supports a ratchet arm such that the carrier and ratchet arm rotate together with the cylinder plug. A free end of the ratchet arm operatively engages the internal toothed portion of the cam tube to rotate the cam tube with the cylinder plug in one rotational direction only. Each cam ring includes a spring plunger arranged to engage one of the plurality of slots in the cam tube upon alignment therewith to cause the cam rings to rotate with the cam tube and cylinder plug to scramble the cam rings either as the cylinder plug is rotated away from its reference orientation during unlocking or back to its reference orientation during relocking.
The lock apparatus preferably allows the combination to be easily changed without the need to disassemble the lock apparatus. Since the combination is determined by the specific driving orientation between the dial and first cam ring as defined by a drive pin coupling these parts, this driving orientation can be adjusted through axially directed separation against a spring bias and relative rotation between the dial and first cam ring to reset the drive pin within a different one of a plurality of angularly spaced drive holes in the coupled part.
The lock apparatus of the present invention is sized for incorporation or retrofit into a doorknob, deadbolt or other lock mechanism. For example, the lock apparatus of the present invention could be used in lockers, desks, or other settings.